The invention relates to a pipe-laying vehicle having a lower vehicle body, a driver""s cab or driver""s stand, a jib, which possesses at its outer end a sheave head with a sheave, and having drive mechanisms for movement, for raising and lowering the jib and for winding up and unwinding the supporting cable running over the sheave.
Such a pipe-laying vehicle, which is used in the constriction of pipe lines laid below the surface of the earth, is known. In such vehicles, the jib, articulated on the lower vehicle body by means of a horizontal axle, can be displaced only within a vertical plane which is determined by the vehicle. The alignment of the pipes, supported essentially horizontally by the jib, is performed by appropriate manoeuvring of the lower vehicle body. The sheave head, in which a deflection pulley for the supporting cable and the upper sheave of a block and tackle are mounted, is fixedly connected by welding to the outer end of the jib. A consequence of this rigid connection of the sheave head to the jib is that the sheave head and the two sheaves mounted therein are always situated in the vertical plane in which the more or less steeply inclined jib also extends. In order, when suspending the load, to orient the sheave head towards the pipe to be suspended and, moreover, to set down the pipe in the intended position of installation, it is therefore necessary for the jib to be brought into an appropriately oriented position by manoeuvring the pipe-laying vehicle. This working procedure, in which the pipe-laying vehicle also has to be moved and manoeuvred when the pipe to be laid is to be turned only through a small angle relative to the ground or is not located approximately vertically below the sheave head, is elaborate and time-consuming.
Accordingly, the object of the invention is to design the pipe-laying vehicle in such a way that it is better adapted to the requirements to be met and permits simpler and more rapid working.
This object is achieved, according to the invention, in that the jib can be swivelled by means of a swivel drive relative to the lower vehicle body about a pivot axis standing perpendicular to the lower vehicle body and in that the sheave head is mounted to swivel on the jib about an adjustment axis.
The swivelling according to the invention of the jib about a vertical axis, which is expediently achieved by supporting the jib on the lower vehicle body via a live ring, offers the possibility, with the vehicle stationary and, if appropriate, stabilized, of laying pipes within a circumference determined by the range of the inclinable jib and aligning them with a pipe trenchxe2x80x94which is done by the interplay of swivel movements and changes of inclination of the jib and winding up or unwinding the supporting cable. The swivelling of the sheave head relative to the jib allows limited swivelling of the sheave head to left or right, out of the vertical plane of the jib, in order to set the sheave head for a load located off to one side on the ground, so that this load can easily be suspended from the jib and pulled across the ground to the vertical plane of the jib. The automatic.setting of the swivelling sheave head for the load to be suspended, or its position, also has the particular advantage that the supporting cable extends from the sheave head towards the load in a direction which deviates to a lesser extent, if at all, from the sheave plane. As a result, the friction between the supporting cable and the sheaves is reduced and smooth running of the cable over the sheaves is enhanced, without any cause for fear that the cable may jump out of the circumferential grooves of the sheaves. When the lifted pipe is set down, also, this can be more simply and reliably controlled under the action of transverse forces, enabling it to be set down wholly or partially outside the plane of the jib. Accordingly, the swivelling of the sheave head relative to the jib also simplifies the work of pipe laying.
However, the swivelling of the sheave head is not always desirable. Consequently, a further development envisages assigning to the sheave head a locking device which permits the fixing of the sheave head in its central position or in a position swivelled out of this central position to one side or the other.
This locking device may be so designed that it simultaneously restricts the swivelling of the sheave head to a particular angular range. The actuation of the locking device may be mechanical, hydraulic or pneumatic. The hydraulic blocking and releasing of the locking device suggests itself if a hydraulic device is already present to actuate the jib of the pipe-laying vehicle, particularly since convenient remote actuation of the locking device can also be achieved in this manner.